Oil cracking system



Jan. 21, was. A, G, PEfERKm JR 2,028,728

OIL CRACKING SYSTEM Original Filed May 6, 1929 VAPOR/ZINE H/Ef/ PRESSURE PUMP INVENTOR ALBERTGPETE/P/fl/VJIZ BYU AM ATTORNEY atented Jan. 21, 1936 ATE T 011. CRACKING SYSTEM Original application May '6, 1929, Serial N0.

360,859. Divided and this application March 3, 1933, Serial No. 659,451

21 Claims. (01.196-60) My invention relates to the art of converting or cracking hydrocarbon oils to produce lower boiling oils, such as gasoline, which are suitable for use as fuel for internal combustion engines. More particularly my invention relates to the cracking of hydrocarbon oils by a combined liquid and vapor phase cracking process.

This application is a division of my copending application Serial No. 360,859, filed May 6, 1929.

In accordance with my-invention, a relatively high boiling oil, as for example, gas oil, is first cracked while the oil is largely in the liquid phase, to form gasoline, a heavy distillate which may be further cracked, an intermediate distillate whose volatility is too low for motor fuel but which may also be further cracked by subjecting it in the vapor phase to suitable cracking conditions, and a residual oil.

More particularly in accordance with my invention, the vapors produced during that portion of the operation in which oil in the liquid form is cracked, are dcphlegmated or fractionated to separate them into fractions, one of which comprises vapors which when condensed will form a suitable fuel for internal combustion engines, an-

other which comprises heavy stock which may be.

recracked under liquid phase cracking conditions, and a third which comprises a stock not so heavy withdrawn from the dephlegmator'and further cracked by subjecting it in the vapor phase to a cracking operation in a suitable portion of the system.

The temperature at which vapor phase cracking is effected is usually in excess of 1000 F. while that at which liquid phase cracking is effected is usually of the order of from 750 F. to 950 F. The stock most desirable for cracking in vapor phase is one which completely vaporizes without leaving a residue.- In case there is incom- Dlete vaporization, that portion thereof which does not vaporize will, due to the high temperature to which the oil is subjected, be converted to a large extent into solid carbonaceous material or coke, at least some of which will deposit upon the interior of the sill and impair heat transfer to that portion of the oil which occurs as vapors therein. For this reason. a charging stock which is particularly suited for my operation is one which has a dry point of not more than 600 F., when distilled by A. S. T. M. Assay Distillation Test No. D 86-27.

Kerosene as produced directly from crude petroleum by distilling in the ordinary way withfor a vapor phase cracking system because usually the stock occurs.

directly with the tubes 3 by means of the pipe 2.

after such fraction is produced it is for a. time placed in storage where polymerization of contained unsaturated compounds takes place with consequent formation of higher boiling compounds which upon being heated in the tubes of 5 the vapor phase cracking system will not readily vaporize and will therefore produce coke in the still.

An object of my invention is to produce by cracking a suitable vapor phase charging stock and immediately subject it, before the unsaturated compounds therein have had an opportunity to polymerize, to vapor phase cracking conditions,

whereupon substantially complete vaporization of My invention resides in a method and apparatus of the character hereinafter described and claimed.

For an understanding of my invention and to illustrate one form of apparatus in which my process may be carried out, reference is had to the accompanying drawing which is a diagrammatic elevational view, partially in section.

Referring to the drawing, A is a furnace having two combustion chambers Al and A2 equipped with the burnersal and a2 respectively. The combustion chambers are provided with the bridge walls bl and b2 respectively, and between these bridge walls is a section A3 of the furnace which is not directly exposed to the heat of combustion of the fuel burned in the chambers Al and A2. With the section A3 there connects the flue j which leads to the stack S. The chambers Al and A2 are provided with banks of radiantly 85 heated tubes I and 2, respectively, while the section A3 of the furnace is equipped with a bank of tubes 3 which is so placed that it may be subjected to convection heat. The tubes 2 connect With the outlet end of the tubes 2 communicates 40 the pipe 4 equipped with pressure reducing valve 5 and connecting at its other end with the vaporizing chamber B. A cooling coil 30 is arranged within the upper portion of the chamber B with an inlet and an outlet passing exteriorly thereof, through which either oil, water or other suitable cooling medium is passed. From the upper portion of the vaporizing chamber, pipe 6 leads to a heat exchanger H which in turn is connected by line I to the fractionating column C. The fractionating column is provided with any suitable fractionating devices, which, in the example illustrated, comprise bubbler plates 8 having vapor uptakes 9 equipped with caps l0, and downflow pipes ll.

Both vaporizing chamber B and fractionating column C, are covered by suitable heat insulating material to effect heat economy. However, it is to be understood that such insulation is not absolutely essential. a

From the top of column C there leads a pipe l2 to the condenser D, in turn connected by pipe l3 to reflux, drum E from which trapped line I4 leads back to the upper portion of the fractionating column C and from which line I5 leads to the gas separator F. The gas separator connects with valve controlled tines I6 and I1 through which may be drawn 0E uncondensed gas and'liquid, respectively.

Line I 8, equipped with high-pressure pump l9 and booster pump I8, conducts liquid oil to the changer through line22 is conducted therefrom through the line 24 to the inlet end of the radiantly heated tubes I. With theoutlet end of' the tubes I communicates the pipe 25, equipped with a suitable valve 25', leading into the lower part of vaporizing chamber B.

The line 26 connects the lower portion of chamber B with the cooler KgWhlCh in turn is connected by valve controlled line'21 to a suitable storage tank (not shown). Communicating with the chamber 13 intermediate its upper and lower ends is line 28, equipped with pump 29, serving to conduct fresh charging stock, as for example, crude oil, to chamber B. There is also provided the manhole M in the lower part of chamber B.

In carrying out my process in the apparatus just described, a suitable fuel, for example, gas, is supplied to and burned at burners al and 112. The products of combustion heat the tubes I and 2 by radiation, then pass over the bridge walls: bl and b2 and serve to heat the tubes 3 by conv-ection, thereafter passing through the flue f to the stack S.

A relatively heavy charging'stock, for example, gas oil of about 25 A. P. I. gravity, which due to its relatively high boiling point is unsuitable as a charging stock for a vapor phase cracking opera tion, is fed under pressure, as for example of about 800 pounds per square inch gauge supplied by pump I9, through the line It into the tubes 3 of the furnace. Upon passing from the tubes 3 the oil is conducted through the line 2' into the tubes 2. During its passage through tubes 2 a portion of the oil is converted into lower boiling components. From the tubes 2, the heated oil is conducted through the iine 4 to the vaporizing chamber B, the pressure upon such oil being reduced as it passes through the pressure reducing valve 5. In the chamber B, due to the reduced pressure, which for example, may be atmospheric or a materially reduced superatniospheric pressure, as for example, of the order of 30 pounds per square inch gauge, portions of the oil are vaporized and are conducted from the upper por-= tion of the chamber through the line 6 to the heat exchanger H. Control 01 the temperature of the with any condensed portion thereof which forms in the exchanger are conducted from the exchanger H through line 'Iinto the lower portion "of the iractionating column C. l

the fresh stock charged through line l8, to the heating tubes 3.

The vapors introduced into the column C through line I pass upwardly therethrough couritercurrent to and in contact with reflux liquid which gravitates downwardly from plate to plate.

Heat interchange takes place between the reflux liquid and the vapors, thereby eflecting progressive change In composition of both the liquid and the vapors, the vapors increasing in lower boiling components as they pass upwardly and the liquid increasing in high boiling components as it passes downwardly through the column. As a result, the boiling range of the individual pools of liquid on the various plates in the column is progressiveiy higher toward the lowerend of the column, so that if portions of the liquid be drawn oil from plates at different levels in the column, such liquid fractions will vary widely from each other in range of volatility.

Those vapors which remain uncondensed throughout their passage through the fractionating cciumn C are conducted through line l2 into condenser D where they are liquefied. The liquid flux liquid, and the other of which is conducted through line It to the gas separator F. In the gas separator the uncondensed gases are removed from the liquid oil and are conducted through valve controlled line It to suitable gas storage, while the liquid is conducted through line H to suitable storage.

Liquid which collects on an intermediate plate 9 at the desired level in the fractionating columnC, is withdrawn through line 22 and is passed therethrough into heat exchanger H where it acts as a cooling medium for the vapors passed into the exchanger through the line 6, the liquid itself absorbing heat. When the liquid has served its purpose in the heat exchanger H or has been raised to the desired temperature, it is conducted through line 24 to the tubes I in combustion chamber Al.

The drawofi pipe 22 communicates with that plate 9 in the column upon which collects liquid whose volatility is such that it will substantially compietely vaporize upon being passed through the radiantly heated tubes I. While only one drawefi 22 is shown, other drawofis maybe provided at different elevations or levels in the column so that lighter or heavier fractions may be withdrawn and passed to tubes I, if desired.

The liquid withdrawn from the intermediate plate in the fractionating column C through pipe 22 is accordingly passed into the tubes I before sufilcient time has elapsed to permit appreciable polymerization to occur with resulting Iormation of high boiling constituents which wouid not readily vaporize in the tubes I.

In passing through the tubes I the liquid, which has taken up some additional heat in the heat exchanger H, is further heated, whereupon substantially complete vaporization occurs, and the vapors are then subjected to high temperatures, as for example, of the order of 1050 F., which efiects substantial cracking of the oil while in vapor phase. By thus utilizing as charging stock I to the tubes I, the low boiling material of that by means of the valve in the line 25 and the 7 pump 23 in line 22, a higher pressure may be maintained in the tubes I, if desired.

The cracked products from the tubes I are introduced through the line 25 into the chamber B, preferably below the level at which. the products resulting from the treatment carried out in the tubes 2 are conducted thcreinto through the line i, so that the cracked products from the tubes I in passing through the chamber B may effect vaporization of additional quantities of the liquid passed into the chamber from tubes 2 due to the partial pressure of the cracked vapors from tubes I in contactwith such liquid, and also due to the sensible heat in the vapors which are at a temperature higher than that of the liquid, and which, therefore, serve further to heat such liquid. As previously stated, the liquid oil which collects in the lower portion of the fractionating column C may be conducted while hot through the line 20 to the line I8. Such oil passes with the fresh charging stock, which for example, may be gas oil, into the tubes 3 through the line I8, under pressure, as hereinbefore stated.

Heavy oil such for example, as crude oil, containing components whose boiling point is so high as to make them unsuitable for cracking in the ;liquid phase, may be fed to the chamber B preferably after having been preheated, as for example, by using it as cooling medium in the cooler K, whereupon vaporization of such portion as is suitable for cracking in the liquid phase is effected, there being left as liquid in the chamber B that portion of the heavy oil which is unsuitable for cracking in the liquid phase in mixture with the residual oil resulting from both the liquid phase and the vapor phase cracking operations. However, it will be understood that the temperatures and pressures in the system may be so regulated as to produce or cause the formation of coke in chamber B instead of allowing a heavy liquid residue to collect in and be drawn off from the lower portion of the chamber. In such case cleaning of the coke from the chamber is effected through manhole M. Y

In the apparatus illustrated the arrangement I of tubes or banks of tubes I, 2 and 3 in the furnace A permits the recovery inthe tubes 3 of the excess heat in the products of combustion after such products have served to heat the tubes I and 2. .The high temperature required to heat the oil in the vapor phase in tubes I to produce cracking results in a high heat content in the products of combustion as they pass from the furnace into the flue f and stack S. It is there- 'fore advantageous; to use some means such as ess is particularly advantageous in that it utilizes heat which would otherwise be lost, to raise the charging stock to be cracked in the liquid phase to substantially its cracking temperature, which heat would otherwise have to be supplied to the system from an outside source.

One of the advantages of my process is that among the products resulting from the liquid phase cracking operation there is produced a distillate, which, while it does not have a volatility suflicient to permit its use as a motor fuel, may be used as charging stock for the vapor phase cracking operation, since it may be completely vaporized and converted by such operation into products of such characteristics as will adapt them for use as a. motor fuel.

A further advantage of my process is that there is effected a mixture of the vapors of the lighter products, or those which are to form the final motor fuel, which result from both the liquid phase and vapor phase operations. Any reaction which would ultimately take place between them, if mixed as liquids will therefore be accelerated due to the relatively high temperature of the vapors. the products are still in the vapor phase, any high boiling products resulting therefrom may be separated from the lower boiling portion by fractionation, while other reaction products are removed by the usual chemical treatment, so that the final product is a substantially stable material. Furthermore by conducting the cracking of a portion of the oil in the vapor phase the final product has a higher antidetonating value than the product which would be obtained by efiecting all the cracking in the liquid phase.

In the use of the terms liquid phase" and vapor phase herein, the commonly accepted meaning of such terms applies. Such terms are not meant to convey that absolutely all of the substance is in the one phase or the other. It is to be understood that herein the meaning of liquid phase cracking is an operation carried out at a considerable pressure, generally in excess of 150 pounds per square inch gauge, and at temperatures of the order of from 750 to 950 F., whereby the density of the material passing through the tubes is maintained relatively high; while the meaning of vapor phase cracking is an operation carried out under lower pressure, as for example, from atmospheric to pounds per square inch gauge, and at higher temperatures, for example in excess of 1000 F., whereby the density of the material passing through the tubes is much lower.

While the heating tubes I and 2 are subjected to a certain amount of convection heating, the principal source of heat is by radiation from the incandescent gases and from the walls of the furnace. In the same manner, tubes 3 are subjected primarily to convection heating by contact with the hot gases passing from the combustion chamber AI and A2 to the flue f; the quantity of heat supplied by radiation to the tubes 3 is a relatively small percentage of the total heat received by them. In the appended claims, the terms convcctively and radiantly as applied to the heating tubes, are used in a broad sense to indicate the major type of heating to which the respective tubes are subjected and not in the sense of excluding incidental heating effected by other means.

What I claim is:

1. A heating apparatus for hydrocarbon fluids comprising a unitary furnace provided with two Since the reaction occurs while separately fired fire chambers and a convection veying 011" being heated by furnace gases from chamber adapted'to receive furnace gases directly from each of said fire chambers, a coil for heating a stream of hydrocarbon fluid passing therethrough to a conversion temperature and consisting of a section mounted in the convection chamher and heated by convection heat from the furnace gases and another section positioned in a radiant heating zone in one of the fire chambers and heated preponderantly by radiant heat therein and a second coil for heating a separate stream ofhydrocarbon fluid positioned in a radiant heating zone in the other fire chamber and heated preponderantly by radiant heat.,

2. A heating apparatus for hydrocarbon fluid comprising a unitary furnace provided with two separately fired fire chambers and convection chamber disposed between said fire chambers to receive furnace gases directly from each fire chamber, a coil for heating a stream of hydrocarbon fiuid passing therethrough to a conversion temperature and consisting of a section mounted in the convection chamber and heated by convection heat from the furnace gases and oils which comprises a plurality of separately fired fire chambers, conduit elements .of restricted cross-section disposed in each of said fire chambers adapted to be heated preponderantly by radiant heat from furnace gases therein, means for simultaneously passing a separate stream of oil through the conduit elements disposed in each of said fire chambers to heat at least one of said streams to cracking temperature, a convection chamber disposed to receive furnace gases directly from each of said fire chambers and conduit elements for conveying one of the streams: of oil to be heated connected to the conduit elements in one of the separately firedl fire chambers, said conduit elements being disposed in said convection chamber in the path of the .furnace gases from each fire chamber to thereby be heated by convection heat therefrom.

4. An apparatus for heating hydrocarbon oils which comprises a unitary furnace provided with a plurality of bridge walls disposed therein to form a plurality of fire chambers, a convection chamber disposed to receive furnace gases flowing around the bridge walls directly from said fire chambers, heat absorbing tubes disposed in said fire chambers and said convection chamber, those in the fire chamber being heated preponderantly by radiant heat, means for connecting tubes in the convection chamber with tubes in one of the fire chambers and means for forcing "ta. separate stream of oil through the heat abeach of said fire chambers and means forconnecting the conduit elements in the convection chamber to conduit elements in one of the fire chambers.

6. A unitary furnace for heating hydrocarbon oils which comprises a plurality of fire chambers, conduit elements for conveying oil being heated to cracking temperature disposed immediately adjacent the roof of each of said fire chambers adaptedto be heated preponderantly by radiant heat from furnace gases therein, a convection chamber disposed between and connected to said fire chambers to receive furnace gases directly from each fire chamber, conduit elements in said convection section for conveying oil being heated by furnace gases from each of said fire chambers and means for connecting the conduit elements in the convection chamber to conduit elements in one of the fire chambers.

'7. Oil treating apparatus comprising a bank 1 radiantly heated tubes substantially outside he path of the convection gases, a bank of convectively heated tubes in series therewith, a second bank of radiantly heated tubes substantially outside the path of the convection gases, means for passing oil into and through said series ,of'

banks of tubes, a chamber, means for passing oil from said series of banks of tubes into said chamber, a dephlegmating column, means for passing vapor from said chamber into the dephlegmating column, means intermediate the upper and lower portions of said column for withdrawing liquid therefrom, and means for passing the liquid so withdrawn into said second bank of radiantly heated tubes.

8. Oil treating apparatus comprising a bank of radiantly heated tubes substantially outside the path of the convection gases, a bank of convectively heated tubes in series therewith, a second bank of radiantly heated tubes substantially outside the path of the convection gases, means for passing oil into and through said series of banks of tubes, a chamber, means for passing oil from said series of banks of tubes into said chamber, a dephlegmating column, means for passing vapor from said chamber to the dephlegmating column, means intermediate the upper and lower portions of said column for withdrawing liquidtherefrom and for passing it into said second bank of radiantly heated tubes, and means for passing products from said last mentioned bank of tubes into said chamber.

9. Oil treating apparatus comprising a bank of radiantly heated tubes substantiallyoutside the path of the convection; gases, a bank of convectively heated tubes in series therewith, a second bank of radiantly heated tubes substantially outside the path of the convection gases, means for passing oil into and through said series ofbanks of tubes, a chamber, means for passing oil from said series of banks of tubes into said chamber,

a dephlegmating column, means for passing vapor from said chamber into the dephlegmating column, means intermediate the upper and lower portions of said column for withdrawing liquid therefrom and for passing it into said second bank of radiantly heated tubes, means for passing products from said last mentioned bankyf tubes into said chamber, and means for withdrawing oil from the lower portion of said column and passing it into and through said series of banks of tubes.

10. The process of converting relatively highboiling hydrocarbon oil to lower boiling oil, which comprises, subjecting the high boiling oil to cracking temperature while passing under pressure in a stream of relatively smallcross-sectional area through zones of a furnace which are respectively convectively and radiantly heated, in-' troducing the cracked oil directly into a vaporizing zone, conducting vapors from said vaporizing zone to a fractionating zone wherein there are separated a series of liquid fractions of progressively increasing volatility, removing from an intermediate point in said fractionating zone a liquid fraction having lower volatility than gasoline but which will substantially completely vaporize under vapor-phase cracking conditions, substantially completely vaporizing said fraction and heating it to cracking temperature while passing in a stream of relatively small crosssectional area through a second radiantly heated zone of said furnace wherein it is subjected to substantially only radiant heat, and thereafter directly introducing the cracked products into the said vaporizing zone.

11. The process of converting relatively highboiling hydrocarbon oil to lower boiling oil which comprises, subjecting fresh charging stockv comprising high boiling oil to cracking temperature while passing under pressure in a stream of relatively small cross-sectionalv area through zones of a furnace which are respectively convectively and radiantly heated, introducing the cracked oil into a vaporizing zone, conducting vapors from said vaporizing zone to a fractionating zone wherein there are separated a series of liquid fractions of progressively increasing volatility, removing from an intermediate point in said fractionating zone a liquid fraction having lower volatility than gasoline but which will substantially completely vaporize under vapor-phase cracking conditions, substantially completely vaporizing said fraction and heating it to cracking temperature while passing in a stream of relatively small .-cross-sectional area through a second radiantly heated zone of said furnace, wherein it is subjected to substantially only radiant heat, introducing the cracked products into the vaporizing zone, and conducting liquid from the lower end of said fractionating zone through the said convectively and first-named radiantly heated zones, in admixure with the said fresh charging oil.

12. The process of converting relatively highboiling hydrocarbon oil to lower boiling oil, which comprises subjecting fresh charging stock comprising high-boiling oil to cracking temperature of from 750 to 950 F. while passing it under pressure in-a stream of relatively small crosssectional area through zones of a furnace which are respectively convectively and radiantly heated, introducing the cracked oil into a vaporizing zone, conducting vapors from said vaporizing zone to a fractionating zone wherein there are separated a series of liquid fractions of progressively increasing volatility, removing from an intermediate point in said fractionating zone a liquid fraction having lower volatility than gasoline but which will substantially completely vaporize under vapor phase cracking conditions, substantially completely vaporizing said fraction and heating it to .a cracking temperature in excess of 1000" F. while passing in a stream of relatively small cross-sectional area through a second radiantly, heated zone of said furnace, wherein it is subjected to substantially only radiant heat, introducing the cracked products into the vaporizing zone, and withdrawing from said fractionating zone a heavier fraction and passing it in admixture with said fresh charging oil stock through the said first named convectively and radiantly heated zones.

13. The process of converting relatively highboiling hydrocarbon oil to lower boiling oil, which comprises, subjecting high boiling oil to cracking temperature while passing under pressure in a stream of relatively small cross-sectional area through zones of a furnace which are respectively convectively and radiantly heated, introducing the cracked oil directly into a vaporizing zone, conducting vapors from said vaporizing zone to a fractionating zone wherein there are separated a series of liquid fractions of progressively increasing volatility, removing from an intermediate point in said fractionating zone a liquid fraction having lower volatility than gasoline but which will substantially completely vaporize under vapor phase cracking conditions, substantially completely vaporizing said fraction and heating it to cracking temperature while passing in a stream of relatively small cross-sectional area through a third heating zone in a furnace wherein it is subjected to substantially only radiant heat, and thereafter directly introducing the cracked products into the said vaporizing zone.

14. A unitary furnace for heating a plurality of streams of hydrocarbon fluids which comprises a plurality of separate fire chambers, an independent source of radiant heat for each of said fire chambers, a convection chamber in open and unobstructed communication with said fire chambers to receive furnace gases from said fire chambers, a bank of tubes for heating hydrocarbon fluid passing therethrough to a conversion tempera ture disposed in one of said fire chambers sub stantially outside the path of the hot combustion gases to be heated to a conversion temperature by radiant heat therein, another bank of tubes disposed in another of said fire chambers substantially outside the path of the hot combustion gases to be heated by radiant heat therein and a bank of tubes disposed in said convection chamber to be heated by furnace gases therein received from the fire chambers.

15. A unitary apparatus for heating hydrocarbon fluids which comprises a furnace provided with a plurality of bridge walls formed to provide a plurality of fire chambers and a convection chamber in open and unobstructed communication therewith to receive furnace gases from said fire chambers, an independent source of radiant heat associated with each of said fire chambers,

a bank of tubes for heating hydrocarbon fluid passing therethrough to a conversion temperature disposed in one of the fire chambers substantially outside of the path of the hot combustion gases to be heated to conversion temperature by radiant heat therein, another bank of tubes disposedin another of said fire chambers substantially outside the path of the hot combustion gases to be heated by radiant heat therein and another bank of tubes disposed in said convection chamber in through to a conversion temperature disposed in one of said separate radiant heating chambers to be heated to a conversion temperature prepon- 'derantly by radiant heafiitherein, another bank of tubes disposed in another of said separate radiant heating chambers to be heated preponderantly by radiant heat thereima bank of tubes disposed in said convection chamber to be heated by furnace g'ases therein and means for connecting said 10* bank tubes in the convection chamber with a bank of tubes in one of said separate radiant heating chambers. 1 17. The method of treating hydrocarbon fluids,

in a furnace comprising a plurality of separate combustion chambers, each of which is provided with an; independent source of radiantdieat am a conduit element therein disposed to be heated by said radiant heat and positioned substantially outside the path of the hot combustion gases, and a convection chamber in open and unob- 'structe-d' communication with" said combustion chambers to receive the furnace gases therefrom, and provided with a conduit element therein disposed-in the path of the furnacegases therein,

that comprises heating a plurality of streams of Whydrocarbons' by passing one stream of hydrocarbons through said onduit element in one of said combustion chambers tothereby heat the stream during at leastf a portion of its flow by radiant heat from said independent source'thereof in said combustion chamber, passing another 7 stream of hydrocarbons through another of said it conduit elements disposed in another combustion chamber to thereby heat the latter stream during at least a portijlin of its flow by radiant heat from said independent source thereof in the latter combustion chamber and applying heat to one of said streams by passage through said conduit element disposed in said convection chamber to I 4?) be heated by the convection gases therein. r

' 18. The methodof heating hydrocarbon fluids,

' in arfgirnace comprising a plurality cf-separate f combustion chambers, each of which is provided with an independent source of radiant heat and a bank of tubes disposed therein to 'be heated i by said radiant heat and positioned substantially outside the path of the hot combustion gases, j and a convection chamber in open and'unob- 1 structed communicationv with; said combustion chambers to receive, furnace gases therefrom that comprises passing a stream of hydrocarbons through one of said banks of tubes in one of said combustion chambers to thereby subject said stream to a conversion temperature by means of radiant heat fronfr the source thereof associated with said combustion chamber, passing another stream of hydrocarbons through another of said banks of tubesgdisposed in another of said combustion chambers to thereby subject said stream to a conversion temperature by means of radiant heat irom the source thereof associated with the latter combustion chamber and heating at least one of said streams of hydrocarbons in said convectigon chamber by convection gases therein. 'i Q;

19.;JI'he method of heating hydrocarbon fluids. in a giurnace comprising a pluralityof sepaifate combiistion chambers, each of which is provided 7 within independent source of radiant heat and to a bank of tubes disposed therein to: be heated by said radiant heat and positioned siibstantially outside the path of the hot combustion gases,

and a convection chamber in openjand unobstructed communication with said combustion absence chambers to receive the furnace gases therefrom and provided with a bank of convection tubes disposed in the path of the furnace gases therein, thatcomprises passing a stream of hydrocarbons through one of said banks of tubes in one of same-combustion chambers to thereby subject said stream .to a conversion temperature by means of radiant'heat from the source thereof associated with: said combustion chamber and heating another stream of hydrocarbons to a conversion temperatureby passing said stream through said bank of convection tubes disposed in said convection chamber to thereby subjectisaid stream to the heat of. convection gases therein and through another of said banks of tubes disposed in another of said combustion chambers to thereby subject said stream to radiant heat from the source thereof associated with the latter combustionrchamber.

20. The method of heating hydrocarbon fluids, in a furnace comprising a plurality of separate combustion chambers, each of which is provided with an independent source of radiant heat and a bank of tubes disposed therein to be heated by said radiant heat and positioned substantially outside the path of the hot combustion gases, and

a convection chamber in open and unobstructed communication with said combustion chamber to receive the 'fumace gases therefrom and provided with a bank of convection tubes disposed in the path of the furnace gases therein, thatconiprises introducing a stream of hydrocarbons to true of said banks of tubes in one of said combustion chambers to thereby subject said stream to a conversion temperature bymeans of'ra-diant with the latter combustion chamber.

21. The method of heating hydrocarbon fluids in a furnace comprising plurality of separate combustion chambers, each of which is provided with an independent source of radiant heat and a bank of tubes disposed thereinto be heated by said radiant heat and positioned substantially outside the path cf the hot combustion gases, and a conveotionrhamber in open andunobstructed communication with said combustion chamber to receive the furnace gases therefrom and provided with a bank of convection tubes disposed in the path of the furnace gases therein, that comprises passing hydrocarbon fluid through one of said banks of tubes 'in one of said combustion chambers to thereby subject said fluid to aieonversion temperature by means of radiant heat from the source thereof associated with said combustion chamber, passing hydrocarbon fluid through another of said banks of tubes disposed in another of said combustion chambers to there by heat said fluid by means of radiant heat from the source thereof associated with said other combustion chamber and simultaneously passing hydrocarbon fluid through said bank of convection tubes to be thereby heated by the furnace gases from said combustion chambers.

Ariana-1: G. PETERKIN, JR.

CERTlFlCATE or CORRECTION.

Patent No. 2,028,728. January 21, 1956.

ALBEBj-I c. PETERKIN, JR.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correctior'f as follows: Page 1, first column, line 45, for the word "sill" read still; page 5, second column, line 58, claim 15, strike out the word "of" first occurrence, page 6,first column, line 22, claim 17, and second column, lines .1, 29 and 56, claims 19, 20 and 21 respectively, strike out the word "the"; same page, second column, lines 28 and 56, claims 20 and 21, respectively, for "'chamberf' read chambers; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 28th day of April, A. D. 1936.

. Leslie Frazer Seal) 2 p Acting Commissioner of Patents. 

